Each year, Arizona emergency departments treat more than 48,000 patients for a traumatic brain injury.

Marc Nielsen suffered a brain injury in 2008, after falling down a flight of stairs at a subway station in Boston.

The injury initially left him with memory loss and loss of peripheral vision.

Those who have a traumatic brain injury may experience sleep problems, low energy, memory loss, anxiety or depression.

Within hours after the first injury, Nielsen experienced two strokes that caused paralysis to the left side of his body.

His life went through a dramatic shift, going from working in Boston to moving to Arizona with his parents.

Nielsen's parents were living in Bangkok when they received the call, and arrived in Boston 30 hours later.

"There was a tremendous amount of care that needed to be given to him to help him learn the basics of life," his father, Tom, said. Nowadays, Tom is also a board member of the Brain Injury Alliance of Arizona.

During his recovery, Nielsen needed to re-learn how to talk, eat and walk.

"I think that it's important to know that caregivers are under tremendous amount of stress," Tom said. "It is so important when caregivers can have support form their family members."

TBI can be especially difficult because it is often an invisible condition. Frequently, people do not know when someone has a brain injury and may not understand the symptoms.

Nielsen said he's been through a number of different types of rehabilitation, which have helped him tremendously.

"I'm currently holding down two volunteer jobs," he said. "One at a place called Home Care Assistance, the other at a place called Tumbleweed, which is an organization that cares for homeless youth."

Also, Nielsen is now a member of a theater production crew called The Improbable Theatre Company.